Buggy code:
private TextView editTextTotal ; private Button incTipButton ; private Button decTipButton ; private Button incSplitButton ; private Button decSplitButton ; private Button calculateButton ; private Button clearButton ; @ Override public void onCreate ( Bundle savedInstanceState ) { } private void init ( ) { setContentView ( tip_calculator ) ; editTextBill = ( ( TextView ) ( findViewById ( R . id . editTextBill ) ) ) ; editTextTax = ( ( TextView ) ( findViewById ( R . id . editTextTax ) ) ) ; editTextTip = ( ( TextView ) ( findViewById ( R . id . editTextTip ) ) ) ; editTextSplit = ( ( TextView ) ( findViewById ( R . id . editTextSplit ) ) ) ; editTextTotal = ( ( TextView ) ( findViewById ( textViewTotal ) ) ) ; incTipButton = ( ( Button ) ( findViewById ( buttonIncTip ) ) ) ; incTipButton . setOnClickListener ( new View . OnClickListener ( ) { public void onClick ( View v ) { try { if ( StringUtils . notEmpty ( editTextTip . getText ( ) . toString ( ) ) ) { Integer tip = new Integer ( editTextTip . getText ( ) . toString ( ) ) ; tip += 1 ; editTextTip . setText ( tip . toString ( ) ) ; } } catch ( Exception e ) { editTextTip . setText ( e . getMessage ( ) ) ; } } } ) ; decTipButton = ( ( Button ) ( findViewById ( buttonDecTip ) ) ) ; decTipButton . setOnClickListener ( new View . OnClickListener ( ) { public void onClick ( View v ) { try { if ( StringUtils . notEmpty ( editTextTip . getText ( ) . toString ( ) ) ) { Integer tip = new Integer ( editTextTip . getText ( ) . toString ( ) ) ; if ( tip > 0 ) { tip -= 1 ; } editTextTip . setText ( tip . toString ( ) ) ; } } catch ( Exception e ) { editTextTip . setText ( e . getMessage ( ) ) ; } } } ) ; incSplitButton = ( ( Button ) ( findViewById ( buttonIncSplit ) ) ) ; incSplitButton . setOnClickListener ( new View . OnClickListener ( ) { public void onClick ( View v ) { try { if ( StringUtils . notEmpty ( editTextSplit . getText ( ) . toString ( ) ) ) { Integer tip = new Integer ( editTextSplit . getText ( ) . toString ( ) ) ; tip += 1 ; editTextSplit . setText ( tip . toString ( ) ) ; } } catch ( Exception e ) { editTextSplit . setText ( e . getMessage ( ) ) ; } } } ) ; decSplitButton = ( ( Button ) ( findViewById ( buttonDecSplit ) ) ) ; decSplitButton . setOnClickListener ( new View . OnClickListener ( ) { public void onClick ( View v ) { try { if ( StringUtils . notEmpty ( editTextSplit . getText ( ) . toString ( ) ) ) { Integer tip = new Integer ( editTextSplit . getText ( ) . toString ( ) ) ; if ( tip > 1 ) { tip -= 1 ; } editTextSplit . setText ( tip . toString ( ) ) ; } } catch ( Exception e ) { editTextSplit . setText ( e . getMessage ( ) ) ; } } } ) ; calculateButton = ( ( Button ) ( findViewById ( R . id . calculateButton ) ) ) ; calculateButton . setOnClickListener ( new View . OnClickListener ( ) { public void onClick ( View v ) { try { <START_BUG> if ( ( ( ( StringUtils . notEmpty ( editTextBill . getText ( ) . toString ( ) ) ) && ( StringUtils . notEmpty ( editTextTax . getText ( ) . toString ( ) ) ) ) && ( StringUtils . notEmpty ( editTextTip . getText ( ) . toString ( ) ) ) ) && ( StringUtils . notEmpty ( editTextTotal . getText ( ) . toString ( ) ) ) ) { <END_BUG> BigDecimal bill = new BigDecimal ( editTextBill . getText ( ) . toString ( ) ) ; BigDecimal tax = new BigDecimal ( editTextTax . getText ( ) . toString ( ) ) ; BigDecimal taxPercent = MathUtils . divide ( tax , BigDecimal . valueOf ( 100 ) ) ; BigDecimal tip = new BigDecimal ( editTextTip . getText ( ) . toString ( ) ) ; BigDecimal tipPercent = MathUtils . divide ( tip , BigDecimal . valueOf ( 100 ) ) ; BigDecimal split = new BigDecimal ( editTextSplit . getText ( ) . toString ( ) ) ; BigDecimal taxedAmount = MathUtils . multiply ( bill , taxPercent ) ; BigDecimal tippedAmount = MathUtils . multiply ( bill , tipPercent ) ; BigDecimal total = MathUtils . add ( bill , taxedAmount , tippedAmount ) ; if ( ( split . intValue ( ) ) > 1 ) { total = MathUtils . divide ( total , split ) ; } total = total . setScale ( 2 , BigDecimal . ROUND_UP ) ; editTextTotal . setText ( ( "$" + ( total . toString ( ) ) ) ) ; } } catch ( Exception e ) { editTextTotal . setText ( e . getMessage ( ) ) ; } } } ) ; clearButton = ( ( Button ) ( findViewById ( R . id . clearButton ) ) ) ; clearButton . setOnClickListener ( new View . OnClickListener ( ) { public void onClick ( View v ) { editTextBill . setText ( "" ) ; editTextTax . setText ( "" ) ; editTextTip . setText ( "" ) ; editTextSplit . setText ( "" ) ; editTextTotal . setText ( "" ) ; } } ) ; }

Fix:
if ( ( ( ( StringUtils . notEmpty ( editTextBill . getText ( ) . toString ( ) ) ) && ( StringUtils . notEmpty ( editTextTax . getText ( ) . toString ( ) ) ) ) && ( StringUtils . notEmpty ( editTextTip . getText ( ) . toString ( ) ) ) ) && ( StringUtils . notEmpty ( editTextSplit . getText ( ) . toString ( ) ) ) ) {